Dynamic expressions of hypothalamic genes regulate seasonal breeding in a natural rodent population

Seasonal breeding is a universal reproductive strategy in many animals. Hypothalamic genes, especially type 2 and 3 iodothyronine deiodinases (Dio2/3), RFamide-related peptide 3 (Rfrp-3), kisspeptin (Kiss-1), and gonadotropin-releasing hormone (GnRH), are involved in a photoperiodic pathway that encodes seasonal signals from day length in many vertebrate species. However, the seasonal expression patterns of these genes in wild mammals are less studied. Here, we present a four-year field investigation to reveal seasonal rhythm and age-dependent reproductive activity in male Brandt's voles (Lasiopodomys brandtii) and to detect relationships among seasonal expression profiles of hypothalamic genes, testicular activity, age, and annual day length. From breeding season (April) to non-breeding season (October), adult male voles displayed a synchronous peak in gonadal activity with annual day length around summer solstice, which was jointly caused by age structure shifts and age-dependent gonadal development patterns. Overwintered males maintained reproductive activity until late in the breeding season, whereas most newborn males terminated gonadal development completely, except for a minority of males born early in spring. Consistently, the synchronous and opposite expression profiles of Dio2/3 suggest their central function to decode photoperiodic signals and to predict the onset of the non-breeding season. Moreover, changes in Dio2/3 signals may guide the actions of Kiss-1 and Rfrp-3 to regulate the age-dependent divergence of reproductive strategy in wild Brandt's vole. Our results provide evidence on how hypothalamic photoperiod genes regulate seasonal breeding in a natural rodent population. This article is protected by copyright. All rights reserved

Effect of AlB2 on the P-threshold in Al-Si alloy

The nucleation of primary Si in Al-Si alloys has been investigated in this work. It was found that there was a threshold concentration of P, below which AlP can not heterogeneous nucleate primary Si in Al-12 wt%Si alloy. AlB2 can not nucleate primary Si directly, but the presence of AlB2 may assist the nucleation of AlP leading to the nucleation of primary Si particles. In addition, with addition of AlB2, the nucleation efficiency of AlP can be improved in Al-18 wt%Si alloy. The orientation relationship between AlB2 and AlP has been calculated, and the adsorption model for AlB2 and AlP was proposed in this work. Keywords: Al-Si alloy, Characterization, Crystal growth, Master alloys, Nucleation, Al

Duplex nucleation in Mg–Al–Zn–Mn alloys with carbon inoculation

Duplex nucleation in Mg–Al–Zn–Mn alloys with carbon inoculation was investigated in this study. Carbon addition brought remarkable grain refinement to both AZ31 (Mg–3Al–1Zn–0.45Mn) and AZ63 (Mg–6Al–3Zn–0.35Mn). Al4C3-coated Al0.89Mn1.11 and Al4C3-coated Al8Mn5 act as the duplex nucleation sites in carbon-treated AZ31 and AZ63, respectively. The morphologies and sizes of dominant Al–Mn phases in both alloys (Al0.89Mn1.11 in AZ31 and Al8Mn5 in AZ63) did not change significantly after grain refinement of the alloys, and these Al–Mn particles are believed to have low nucleating efficiency for primary α-Mg. In contrast, Al4C3, the interfacial phase between primary α-Mg and duplex nucleating particles, is the direct potent nucleating substrate for primary α-Mg

How Can We Overcome the Strength–Ductility Tradeoff in Light Alloys and Related Composites?

In recent decades, the design and development of light alloys and related composites to achieve a good combination of strength and ductility have attracted huge attention [...

Effect of manganese on the microstructure of Mg–3Al alloy

The effect of manganese on the microstructure of Mg–3Al alloy, especially the nucleation efficiency of Al–Mn particles on primary Mg, has been investigated in this paper. Mg–0.72Mn was used to fabricate Mg–3Al–xMn (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) alloys, and the grain sizes of these alloys fluctuate at 390 μm indicating addition of manganese does not evidently influence the grain size of Mg–3Al alloy. Through XRD, FESEM and TEM detection, it is found that Al0.89Mn1.11 compound is the dominant Al–Mn phase in Mg–3Al–0.3Mn, Mg–3Al–0.4Mn and Mg–3Al–0.5Mn, and distributes in primary Mg matrix and interdendritic regions with an angular blocky morphology. The number of Al0.89Mn1.11 increases gradually with increasing manganese content while the grain sizes of primary Mg are nearly the same in Mg–3Al, Mg–3Al–0.3Mn, Mg–3Al–0.4Mn and Mg–3Al–0.5Mn, indicating Al0.89Mn1.11 has low nucleation efficiency on primary Mg

In-situ synthesis and chemical bonding of the Al-doped β-SiC particles in Al-Si-C light alloys

In this work, the Al-doped β-SiC particles are in-situ synthesized in Al-20Si-5C alloys using the novel liquid–solid multiphase reaction method. The morphological evolution with changed Al doped β-SiC particles has been carefully investigated, and it is observed that the β-SiC transforms from the hexagonal flake to the truncated pyramid and finally evolves to the irregular polyhedral with the decrease of Al doping in SiC. The influence mechanism of the Al doped amount of SiC on the Brinell hardness and wear resistance of the Al doped SiCp reinforced aluminum matrix composites has been explored. Furthermore, the density functional theory (DFT) calculations of the chemical structures of doped SiCp with different Al doping levels indicate the covalent bond proportion in SiCp and the electron density around carbon atoms are all decreased as the increase of the Al doping content. It is also found that the Young’s modulus and Vickers hardness of doped SiCp decrease as the Al doping content increases by DFT calculations. It is proposed that this work paves a new way to improve the properties of aluminum matrix composites by regulating the doped level and chemical bonding of reinforcing particles for potential light weighting applications

Merkmalskatalog und komplettes Regelwerk zur Szenariobewertung

Available from TIB Hannover: RN 5527(163) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

A novel Zn-Cu-P master alloy and its modification performance on primary Si of A390 alloy

The requirement of modification on primary Si particles at low temperature has restricted the development of inoculants in low pressure casting industries. In this paper, by dissolving Cu-14P master alloy into Zn melt and utilizing the diffusion of Zn atoms into Cu3P phase, a novel Zn-8.6Cu-1.4P master alloy has been synthesized. Except for η-Zn matrix, ε-CuZn5 and α-Zn3P2 are the main intermetallics. After introducing into A390 melt at a relatively low temperature (≤720 °C), the α-Zn3P2 phase evolves to AlP, and the in-situ formed AlP nucleus exhibits attractive modification performance on primary Si. The Zn-Cu-P master alloy may be a promising candidate for application in low pressure casting industries. Keywords: Casting, Microstructural characterization, Al-Si alloy, Zinc-based alloy

Synthesis of an Al-Based Composite Reinforced by Multi-Phase ZrB2, Al3BC and Al2O3 with Good Mechanical and Thermal Properties at Elevated Temperature

To synthesize Al composite with high strength at elevated temperature, high modulus and thermal stability, ZrB2, Al3BC and Al2O3 particles have been chosen as reinforcements simultaneously. A (9.2 wt.% ZrB2 + 5.6 wt.% Al3BC + 5.5 wt.% Al2O3)/Al composite has been prepared, and the in-situ synthesized particles are nano-sized. Mechanical property tests reveal that the nanoparticles exhibit a remarkable synergistic enhancement effect. The elasticity modulus of the composite is 89 GPa, and the ultimate tensile strengths at 25 °C and 350 °C can be as high as 371 MPa and 154 MPa, respectively